125 years ago, on 10 June 1886, Mt Tarawera erupted without warning. Craters vented fountains of glowing scoria, and a 17-kilometre rift spewed steam, ash and mud over the surrounding area. Nearby settlements were destroyed or buried by hot mud, and about 120 people perished.

A major tourist attraction, the Pink and White Terraces, was one of the casualties of the eruption. The area around the terraces had become a deep crater, which filled with water within a few months to form the modern Lake Rotomahana.

There has long been speculation about whether any part of the terraces survived, but it had been impossible to check deep in the lake. Early this year a joint US–New Zealand team explored the bed of Lake Rotomahana using a small, unmanned submarine. In February they announced that they had found part of the Pink Terraces, but it was then believed that the White Terraces had been destroyed.

However, on the 125th anniversary of the Tarawera eruption, GNS scientist Cornel de Ronde was delighted to announce that detailed analysis of the underwater sonar records had detected hard, crescent-shaped structures on the lake bed at the site of the White Terraces at a depth of about 60 metres. Unfortunately there are no underwater photographs, but there is little doubt that this discovery will lead to renewed exploration of the floor of Lake Rotomahana.

The discovery has special significance for the Tūhourangi people, a sub-tribe of Te Arawa) whose ancestors used to guide visitors around the Pink and White Terraces. Many members of the tribe were killed during the Tarawera eruption, and those who survived settled at Whakarewarewa. The devastated land was later taken over by the Crown, and is now the subject of a claim before the Waitangi Tribunal.